It sounds like you have a Shimano Tiagra triple set-up. I bought a bike with the express notion of changing the small chainring to a 26 tooth. I'd had success with doing that with a Campy triple (24 tooth) in the past. It didn't work with Tiagra. If I adjusted things just right, it would only work marginally. even with a Jump Stop installed, it dropped the chain way too much for my liking. Tiagra is set up to work with a limited range of chainrings in each position. In my opinion, they picked some bad choices for a triple. I wound up changing the whole crankset to a Sugino Alpina II with 48-36-24 chainrings and using a bar-end friction shifter and Alpina derailleur. I'm a shift-o-holic and I had to have STI for the rear but friction shift on the chainrings is fine (if not preferable). For the rear, I replaced the cog set (11-28) with one that has 11-34. This necessitated in my changing the rear derailleur for one that would wrap the extra chain. I used a Deore 9 speed mountain bike derailleur which has the same pull ratio as the Tiagra 10 speed road derailleur. It works flawlessly. You can't use Shimano 10 speed mountain bike derailleurs with Shimano 10 speed road shifters.
This was kind of a round-about way to do it, but I now have the bike that I wanted.